Aging and oxidized proteins: Generation and degradation

It has been suggested that reactive oxygen species (ROS) are involved in the generation of altered proteins that are reported to increase with advancing age. Among chemical modifications of proteins, carbonyls are their useful markers that can be determined and characterized by the spectroscopic and immunological analyses of protein samples derivatized with the carbonyl reagent 2,4-dinitrophenylhydrazine. The age-associated accumulation of altered proteins can be caused not only by the age- related increase in ROS generation, but also by the decline of protein -degradation. In fact, half-lives of proteins including oxidatively modified proteins in cells from old mice were shown to be significantly longer than those in cells from young mice. A decrease in proteasome activity appears to be primarily responsible for an age-related decline in the degradation of oxidatively modified proteins. Importantly, proteasome itself was suggested to alter with age by its decreased specific activity (the activity per intensity of immunological signals for the subunits), thus likely contributing to form a vicious cycle of accumulation of altered proteins.